JS, you are right.
In the last two years, Roger has won only 2000 Big points and Murray has won only 3000 Big points. So, they total only 5000 points.
On the other hand, Stan has won 5000 points and Cilic has won 2000 points. They total 7000 points. So, surely if we replace Murray and Federer by Stan and Cilic, the group's market share goes up. So, even by my own simple criteria outlined, Big Four is gone and history. If I want to salvage, I have to dig deep to 3 years at least. I have not checked the arithmetic on that. But, I completely agree that if we are willing to go back to only two years from the current moment, Big 4 is done.
No, I am not insisting that there has to be some Big Four (not necessarilyt the old one).
It could be Big 3, It could be Big 2, It could be Big 1, It could be Big nothing as well.
However, I think we are in a Big 1 situation as illustrated below.
In the last two years, the members of the old Big 4 have won 29,000 points. But, their distribution is highly uneven.
Novak --- 17,000 pts. ---- 58.62% of the points won by Big 4
Rafa --- 7,000 pts. ---- 24.13% of the points won by Big 4
Andy --- 3,000 pts. ---- 10.34% of the points won by Big 4
Fed --- 2,000 pts. ---- 6.89% of the points won by Big 4.
If all members of the big four contributed equally, each one's percentage would be 25%.
Since, we don't expect uniform contribution, to allow for variation, we could say each one
should have contributed at least 12.5%. But, clearly Andy and Fed are contributing even below that.
Moreover, if we replace Andy & Fed by Stan and Cilic the group's market share increases.
Note also that if we are willing to drop Murray and Fed from Big 4, we still cannot call it as Big 2.
The reason is that if we confine to 2, the market share percentages between them would be
Novak ---- 70.8%
Rafa ---- 29.2%
That is too much of a variance to include Rafa in the group. Rafa is supposed to contribute 50%. As things won't be perfectly even, we should hold him accountable for at least 40% to pull his weight.
As that is not the case, he should be excluded from any BIG groups as well.
The only way to "salvage" big four is by altering the scheme and either going three years deep or giving credit for being a finalist in big events. Fed's ranking points creates an illusion as most of them are won by being a finalist or semifinalist in various events without actually collecting much marbles.
Anyway, the writing is on the wall. The "Big Four" are out, even if not right now, pretty soon.